1. Field of the Invention
The present invention relates to a lock that is utilized for selectively precluding relative movement between the sashes of sliding windows or doors.
2. Description of Related Art
Many types of locking devices have been utilized to prevent relative movement between the sashes of sliding windows or doors, however the most common type of locking device utilized is that of the combination of a pivotal element and associated stationary element. When utilized in a sliding window assembly, the pivotal element is attached to the upper surface of the lower sash of the window and the stationary element is attached to the upper surface of the lower rail of the upper sash of the window. When it is desired to lock the window, the sashes are maneuvered so as to allow a user to arrange the pivotal element so that it engages the stationary element. This conventional arrangement has many disadvantages, some of which are that it detracts from the aesthetic qualities of the window and the pivotal element can be damaged if the user applies an excessive amount of stress to it. A critical disadvantage, however, of the conventional arrangement is that it is substantially visible from outside the window and can be easily disengaged by unauthorized persons if the glass pane is broken from the window.
One attempt at addressing the above-mentioned problems is disclosed in U.S. Pat. No. 3,501,932, issued Mar. 24, 1970 entitled, "Window Lock" to Bishop. That patent describes a plunger-type mechanism wherein a plunger is telescopically received in the upper rail of the inside lower sash and insertable into a receiving space located within the lower rail of the upper outside sash, to prevent relative movement of the upper and lower sashes with respect to each other. The locking element can be moved through the upper rail of the lower inside sash by means of a key that can be selectively retained in the lock or removed from the lock when the plunger is received in the lower rail of the outside upper sash. The plunger and the receptacle of the lower rail of the upper outside sash co-act with each other when the plunger is placed in its locked position so that the upper and lower sashes are drawn toward each other and are placed into alignment with each other.
A disadvantage of the arrangement described in the Bishop patent is that a key is required to lock and unlock the window. If the key is not available, the window cannot be opened. If the key is lost, the user will incur an expense in replacing the lock or the key. Another disadvantage is that the use of the key makes locking or unlocking numerous windows in a large building a time consuming process since typically only a few people will have possession of a key. Another disadvantage is that the locking device might detract from the aesthetic qualities of an ornately and decoratively designed window.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a locking device for locking together the sashes of sliding windows or doors whereby the windows or doors can be locked or unlocked without the use of a key.
It is another object of the present invention to provide a window or door lock that is not totally visible from outside a sliding window or door.
It is a further object of the invention to provide a window or door lock that does not detract from the aesthetic qualities of a sliding window or door.
It is yet another object of the present invention to provide a window or door lock that is of very simple construction.